1. Field of the Invention
This invention generally relates to catheters for use in enabling the visualization of the anatomy and more specifically to catheters that are particularly adapted for the field of endoscopic retrograde cholangiopancreatography.
2. Description of Related Art
The use of catheter-like devices for administering therapeutic, diagnostic and vaso-occlusive agents at predetermined target sites in a patient is well known. Initially catheters of this type, particularly for use in the field of endoscopic retrograde cholangiopancreatography (ERCP) procedures, were constructed from Teflon.RTM. and included a single lumen sized to accommodate a wire guide and to act as a liquid agent transfer channel. As the ERCP catheters typically were also adapted to be inserted over guidewires or through working channels of endoscopes, they were typically shipped with a stylet wire in the lumen that would stiffen the catheter to prevent kinking or bending. The styler had to be removed prior to any use of the catheter with a guidewire or after the catheter was inserted through an endoscopic device.
The presence of a guidewire in the lumen may restrict the transfer of liquid agents, such as radiographic contrast agents, through the lumen past the guidewire. Consequently after a physician inserted the ERCP catheter, any guidewire would be removed to facilitate the administration of a radiopaque contrast agent to determine the location of various obstructions.
Often times it became necessary to reposition the catheter. This required the reinsertion of the guidewire through the lumen to enable catheter relocation. Then it was necessary to remove the guidewire again. The need to maintain sterile conditions further complicated this procedure especially as to the guidewire while it was removed from the catheter. Given the nature of the contrast agents, it was also found that in some cases the contrast agent, guidewire and lumen in combination can become stiff thereby reducing catheter flexibility. In some situations it was even possible for the guidewire to stick in the catheter thereby requiring the removal of both the catheter and the guidewire. Single lumen catheters also were characterized by back flow whereby the contrast agent could squirt back out the proximal end of the catheter and onto the administering medical professional.
More recently there have been introduced dual lumen ERCP catheters in which one of the lumens is adapted for receiving a guidewire or stylet and the other is adapted for transferring the contrast agent. The transfer lumen has typically either had a circular cross-section or crescent-shaped cross-section, the latter being disclosed, for example, in U.S. Pat. No. 5,397,302 to Weaver. In the Weaver patent a catheter formed of polyurethane or nylon has a durometer of about 60 D and a hydrophilic coating thereby to provide lubricity, kink resistance and suppleness. The catheter tube has substantially cylindrical side walls, a proximal end for connection to a source of contrast medium and a distal end for entry into the common biliary duct of a patient. The tube contains a first crescent-shaped liquid agent transfer lumen for transporting contrast media from the source of the contrast medium to the biliary duct. A second circular lumen facilitates the insertion of the catheter over a guidewire.
Although dual-lumen catheters of the prior art eliminate many of the handling problems posed by single lumen catheters, in terms of removing and reinserting a stylet or guidewire, several undesirable characteristics still exist. For example, dual lumen catheters for ERCP procedures are limited to a maximum overall diameter. The addition of a second lumen of sufficient size to provide adequate transfer rates through the catheter of that maximum size can weaken the catheter wall and subject the catheter to being burst while a contrast agent is being administered. Further, even if some minimum wall thickness is maintained to prevent bursting, a catheter being inserted through an endoscope without a guidewire is subject to kinking and bending under the axial pressure required to move the catheter relative to the endoscope. Kinking and bending have a real potential for damage to the catheter. Consequently physicians oftentimes will become quite deliberate and even tentative in advancing a catheter as the transfer force increases in order to avoid kinking or bending with the subsequent requirement that the catheter be withdrawn and destroyed. Consequently even dual lumen catheters typically include a stiffening stylet for use with endoscopic devices. Still further, these constraints on the size of the second lumen can, for reasonable pressures exerted on the liquid agent, limit flow rate through the lumen to an unacceptably low value.